The answer is logical.
Assuming 60FPS, if an object is set to 50000 px per second (which is ridiculous), then in one tick, the object can travel 50000/60 px per tick ( approx 833).
Considering the object that it's meant to collide with is only 20px wide, it's pretty obvious that the chances of a collision are slim, as the speeding object will easily pass by the collision object.
To put it another way: if you had a standard screen size of say 1024x768, then you have set an object to travel at roughly 50 times the screen width every second. I can't envisage there ever being a need for such a thing - it makes no sense.
The answer is to reduce the speed, or increase the collision object, but at the speed you are currently using, I can't see that increasing the collision object being of much use.